Re: [PATCH v6 08/11] tpm: Driver for supporting multiple emulated TPMs

[Stefan Berger]

On 03/09/2016 09:57 PM, Andy Lutomirski wrote:
> On Wed, Mar 9, 2016 at 6:34 PM, Stefan Berger
> <stefanb@xxxxxxxxxxxxxxxxxx> wrote:
> > On 03/09/2016 01:01 PM, Andy Lutomirski wrote:
> > > On Wed, Mar 9, 2016 at 9:39 AM, Stefan Berger
> > > <stefanb@xxxxxxxxxxxxxxxxxx> wrote:
> > > > This patch implements a driver for supporting multiple emulated TPMs in a
> > > > system.
> > > >
> > > > The driver implements a device /dev/vtpmx that is used to created
> > > > a client device pair /dev/tpmX (e.g., /dev/tpm10) and a server side that
> > > > is accessed using a file descriptor returned by an ioctl.
> > > > The device /dev/tpmX is the usual TPM device created by the core TPM
> > > > driver. Applications or kernel subsystems can send TPM commands to it
> > > > and the corresponding server-side file descriptor receives these
> > > > commands and delivers them to an emulated TPM.
> > > Nifty!
> > >
> > > Is anyone considering writing a modification or replacement of
> > > trousers that creates claims the real tpm and exposes a vtpm that
> > > handles multiplexing internally?  Does the vtpm driver intelligently
> > > support multiple simultaneous clients?
> >
> > The vtpm driver allows to use an independent trousers instance in each
> > container.
> >
> > Using the VTPM_NEW_DEV ioctl the container mgmt. stack can create a
> > /dev/tpmX (X=0,1,2,...) device and a file descriptor. The file descriptor is
> > passed to a vTPM instance, the /dev/tpmX is moved into the container,
> > meaning a device with the same major/minor numbers is created in the
> > container. This then allows each container to talk to an independent vTPM.
> > The vTPM can either be 1.2 or 2.
> What I meant was:
>
> If two clients connect to the same vTPM slave node, can the master
> program tell requests from the two clients apart?  If so, great!  If
> not, then I'd consider that to be somewhat sad.

vTPM slave node being /dev/tpmX? TPM types of devices can currently only 
be opened by one application. This can for example be TSS/trousers, 
which then offers an API to applications for sending TPM commands. That 
only one application is allowed is a limitation of the existing driver.

   Stefan